DRIVERS-2713: Run legacy transaction tests on LB topologies

[jmikola]

https://jira.mongodb.org/browse/DRIVERS-2713

d2de77692b727b805168eeba02c3ab29e6a1d3e2 previously added "load-balanced" to other legacy test formats but omitted the transactions spec.

This change ensures legacy transaction tests can be run on LB topologies, including Atlas Serverless (where "serverless: forbid" is not specified).

Please complete the following before merging:

• [x] Update changelog.
• [x] Make sure there are generated JSON files from the YAML test files.
• [x] Test changes in at least one language driver.
• [x] Test these changes against all server versions and topologies (including standalone, replica set, sharded clusters, and serverless).

[jyemin]

I ran these on Java driver and these tests failed for Serverless:

• retryable-commit.json: commitTransaction fails after two errors
• retryable-commit.json: commitTransaction applies majority write concern on retries
• retryable-commit.json: commitTransaction succeeds after connection error
• retryable-commit.json: commitTransaction succeeds after InterruptedAtShutdown
• retryable-commit.json: commitTransaction succeeds after ShutdownInProgress

I'm not sure if this a Serverless issue or a Java driver issue, so I'd like a couple of other drivers to test these changes before merging this. We can always add serverless: forbid to the failing tests and open a ticket against Serverless to address the failures..